If there was no free will, there would be no sin. But there is sin, therefore there is free will.
There is only God’s will in heaven, and therefore is no sin. If a perfect God made perfect creatures, they would be perfect, but not free.
As in Eden , there is God’s will, and our will. And because there was a choice then and is now, the will is free. Not because God doesn’t know the outcome of the decision, but because he allows us to make the decision.
God knows what is going to happen, but still prefers that we choose his will. We have the ability to make a choice outside of his preference. To sin. That is why we’re free.